<h1>DefineJPEGImage3</h1>

<p>DefineJPEGImage3 is used to define a transparent JPEG encoded image. It extends 
the functionality provided by DefineJPEGImage2 by including a separate zlib 
compressed table of alpha channel values. This allows the transparency of 
existing JPEG encoded images to be changed without re-encoding the original image.</p>

<table>

<tr>
<th nowrap>Field Name</th>
<th>Type</th>
<th>Size</th>
<th>Description</th>
</tr>

<tr>
<td nowrap valign="top">type</td>
<td nowrap valign="top">unsigned bit</td>
<td nowrap valign="top" align="right">10</td>
<td>Identifies the DefineJPEGImage3 instruction when it is encoded. It is encoded 
with the length field as a 16-bit integer (Little-endian byte order).</td>
</tr>

<tr>
<td nowrap valign="top">length</td>
<td nowrap valign="top">unsigned bit</td>
<td nowrap valign="top" align="right">6</td>
<td>The length in bytes of the body of the instruction when it is encoded. If the length is greater 
than 62 then this field is set to 0x3F and the length is encoded using the 
extendedLength field. Encoded with the type field as a 16-bit integer.</td>
</tr>

<tr>
<td nowrap valign="top">extendedLength</td>
<td nowrap valign="top">unsigned int</td>
<td nowrap valign="top" align="right">32</td>
<td>Optional. Contains the length in bytes of the encoded instruction if it is
greater than 62 bytes. If the length is 62 bytes or less then this field is 
omitted.</td>
</tr>

<tr>
<td nowrap valign="top">identifier</td>
<td nowrap valign="top">unsigned int</td>
<td nowrap valign="top" align="right">16</td>
<td>The unique identifier for this image definition. This is used when adding or removing 
the shape from the display list or when the shape is used as part of another 
object such as a button.</td>
</tr>

<tr>
<td nowrap valign="top">image</td>
<td nowrap valign="top">byte[n]</td>
<td nowrap valign="top" align="right">&nbsp;</td>
<td>An array of bytes containing the JPEG compressed image.</td>
</tr>

<tr>
<td nowrap valign="top">alpha</td>
<td nowrap valign="top">byte[n]</td>
<td nowrap valign="top" align="right">&nbsp;</td>
<td>An array of bytes containing the zlib encoded alpha channel data for each 
pixel in the image.</td>
</tr>
</table>

<h2>History</h2>

<p>DefineJPEGImage3 represents the DefineBitsJPEG3 tag from the Macromedia Flash 
(SWF) File Format Specification. It was introduced in Flash 3.</p>
